The Great Wall of China is a series of stone and earthen fortifications built by a number of emperors to protect the northern borders against nomadic tribes. At one time the wall stretched from Shanhaiguan on China's east coast through a variety of terrains including mountains, plateaus and desert to Lop Nur in the North West of the country. Today a lot of that wall has disappeared but parts are still being rediscovered, its current length is approximately 4,500 miles.

Although walls have existed in China since the 9th century BC, they were used extensively during the Warring States Period between the 5th century and 221 BC, although it wasn’t until the unification of China by Qin Shi Huangdi, the First Emperor of China that the connection of the various walls was carried out to form a unified defensive system. Qin Shi Huangdi unified China not just politically but also economically by standardizing the Chinese units of measurements, the currency and the Chinese script. He also developed an Irrigation System and an extensive network of roads and canals connecting the provinces in order to improve trade, and he carried out a major development of the Great Wall.

The original wall was constructed mainly of rammed earth, the same methods are used in China today, posts would be placed in the ground, and planks would be positioned and held in place by the posts. Earth would then be placed between the planks and well compacted by pounding. Branches would be laid at stages as a layer as the wall was built up in order to act as a binder. The work force included soldiers, prisoners and peasants who were taken from all over the country and relocated where they would toil for the rest of their lives, millions died in the process and it is thought that one person died for every metre of length that the wall stretches, giving the wall the name of the long grave yard.

The next great building session was carried out by the Ming Dynasty (1368–1644). The first of the Ming Emperors was Hongwu who became emperor in 1368. Before that the country was ruled by the Mongol or Yuan Dynasty but a peasant revolt removed them. The leader of the revolt became emperor and adopted the name Hongwu. He started some of the building work on the wall but it was his son Yongle, who was to become one of the greatest emperors, who carried that on. Yongle moved the capital from Nanjing in the south to Beijing and started fortifying the great wall due to his fear of attack. It was during the Ming period that the modern wall was built stretching from Dandong on the Korean border to Jiayuguan at the end of the Spice Route in the Gobi desert.

The main purpose of the wall was to impede and deter any potential invaders by also serving as a psychological barrier. It also enabled the quick deployment of soldiers through the rugged terrain. Standing 30 feet (9.14 metres) high and 10 feet (3 metres) wide it was one of the greatest engineering feats of all time using the most up-to-date technology with regard the manufacture of bricks to the drainage channels that would direct water to the outfall on the inside of the wall to prevent the enemy from being able to lasso the guttering and prevent water supply to plants which would provide cover to attackers.

The wall enabled troops to be stationed at regular intervals who could signal if an enemy was approaching and could summon help. To this end they used smoke signals during the day and fire signals at night, these were relayed from one watchtower to another; using this system messages could be rapidly sent over great distances. The watchtowers were built at regular intervals along many stretches of the Great Wall. They would also have beacon towers in front of the walls to warn of any advancing army and towers where the garrison could sleep and provide additional protection. There would also be Storehouses and barracks so that any additional troops rushed to the spot to meet an attack could be provisioned. Gates would be placed and manned to control access and egress. The wall served China for several hundred years and was breached only once in 1644 when a Chinese General opened the gates to allow the Manchu to enter after the emperor took his love as a concubine. This brought about the replacement of the existing dynasty with the Qing Dynasty that was to rule China until the 20th century.

Today the Wall can be visited at a number of places, the most popular ones being at Badaling and Mutianyu, which can be visited from Beijing. Access to the wall at Mutianyu is via a cable car. Badaling provides the choice of two routes, a steep and a shallow one, depending on fitness ability. These sections - built around 500 years ago - have undergone extensive renovations by the Chinese government over the last few decades and to gear it up to tourism. Today The Great Wall is a world heritage site and China is aware of its importance as a heritage and tourist attraction and is ensuring that it is maintained.

To see more photographs and take a virtual tour of the site click on the photoshow below.